Harringtonia lauricola Spread in Sassafras Root Systems in the Absence of Its Vector, the Redbay Ambrosia Beetle ( Xyleborus glabratus )
| Authors: | Katy Crout, Julia Kerrigan, Albert (Bud) E. Mayfield, Jess Hartshorn |
| Year: | 2026 |
| Type: | Scientific Journal |
| Station: | Southern Research Station |
| DOI: | https://doi.org/10.1111/efp.70095 |
| Source: | Forest Pathology |
Abstract
Laurel wilt is a vascular disease caused by a non‐native pathogen ( Harringtonia lauricola ) and an associated beetle vector (redbay ambrosia beetle; RAB; Xyleborus glabratus ) affecting several members of the Lauraceae family in North America, including the ecologically and culturally important sassafras ( Sassafras albidum ). Since discovery of the vector in 2002 and the disease in 2004 near Savannah, GA, laurel wilt has spread widely throughout the eastern United States, causing widespread mortality to redbay, sassafras, and other lauraceous species. The objective of this study was to assess the spread of H. lauricola through sassafras roots in the absence of the beetle vector. Four spatially independent forest plots containing sassafras were identified in the Clemson Experimental Forest, and 1–2 mature trees in each stand were inoculated with H. lauricola in May of 2020. All sassafras in each plot were counted and categorized by size class and crown damage over a 4‐year period. Harringtonia lauricola was confirmed in sassafras roots up to 3.6 m from inoculated trees 1‐year post‐inoculation in the absence of RAB. Sassafras stems closer to the inoculated tree experienced greater wilt symptoms and mortality. Despite significant mortality and wilt, nearly 50% of the sassafras stems across all sites were still living 4 years post‐inoculation. These results demonstrate that laurel wilt can spread from one sassafras stem to others via underground movement of the pathogen through root suckers in natural stands, but that many trees can survive years after inoculation. Development of management strategies for laurel wilt in sassafras will need to account for this mechanism of disease spread.